At least substantially metallic cylinder head gasket

ABSTRACT

Cylinder head gasket with a metallic gasket plate comprising a combustion chamber opening enclosed by a bead, and a stopper surrounding the opening and delimiting deformation of the bead, the stopper formed by elevations of a gasket sheet metal layer which are obtained by deformation thereof, the stopper is designed such that in sections through the sheet metal layer along circular cylindrical surfaces coaxial with the opening the stopper comprises a row of discrete elevations following one another in a circumferential direction of the opening and corresponding depressions located directly opposite these elevations, and in a plan view of the sheet metal layer in the area of the stopper, the total area occupied by the elevations is at least half of the total area of the stopper, and the shape of the elevations differs from the shape of circular arcs at least partially enclosing the opening.

This application is a continuation of application Ser. No. 10/052,468filed Jan. 23, 2002, now U.S. Pat. No. 6,769,696.

The present disclosure relates to the subject matter disclosed in Germanapplication No. 101 48 295.7 of Sep. 29, 2001, which is incorporatedherein by reference in its entirety and for all purposes.

BACKGROUND OF THE INVENTION

The invention relates to a cylinder head gasket with an at leastsubstantially metallic gasket plate comprising at least one combustionchamber opening enclosed by at least one bead elastically deformable inits height, and close to the bead at least one deformation delimitingdevice (stopper) likewise enclosing the combustion chamber opening anddelimiting the bead deformation.

In the case of one-layered or multilayer metallic cylinder head gasketsit has so far been customary, in order to produce a stopper radiallyinside or outside (with respect to the combustion chamber opening) ofthe bead carrying out a sealing function, to increase the thickness of asheet metal layer in an area enclosing the combustion chamber opening inthe shape of a circular ring by a flat metallic ring being attached (forexample, by welding) to this sheet metal layer or by an edge area of thesheet metal layer surrounding the combustion chamber opening beingflanged, i.e., folded over through approximately 180°. Such a stopperhas at least almost no elastic properties, and, in most cases, also atleast almost no plastic properties, in any case under the pressureforces exerted on the stopper during operation of the engine.

Single-layered or multilayer metallic cylinder head gaskets haverecently been proposed (WO 98/28559 and DE-U-298 04 534), wherein thestopper is to a considerable extent plastically and/or elastically,preferably predominantly elastically deformable under the pressureforces acting on the stopper during operation of the engine and isdesigned in one of the following ways: The sheet metal layer providedwith the stopper is provided radially within the bead carrying out thesealing function and requiring protection (with respect to thecombustion chamber opening) with one or several beads forming thestopper, enclosing the combustion chamber opening in the shape of a ringand extending concentrically with the combustion chamber opening, and inthe event that there are several beads, these can project alternately inone or the other direction of the axis of the combustion chamber opening(see FIGS. 12A and 12B of WO 98/28559). Alternatively, the stopper isformed by a series of ribs and grooves following one another alternatelyin the radial direction, enclosing the combustion chamber opening in theshape of a ring and being provided on both sides of the sheet metallayer, with the ribs projecting above the two main surfaces of the sheetmetal layer and thus resulting in a thickening of the sheet metal layerin the area of the stopper, each rib on the one side of the sheet metallayer having located directly opposite it a rib on the other side of thesheet metal layer (the same then applies to the grooves), and the ribsand grooves having been produced by extrusion of the sheet metal layer(FIG. 12E of WO 98/28559 and DE-U-298 04 534). These stoppers are easierto manufacture than stoppers attached to a sheet metal layer or producedby flanging a sheet metal layer, as it is possible for a sheet metallayer provided with beads to be punched out and provided with the beadswith a single tool and for a sheet metal layer to be punched out andprovided with the above-described ribs and grooves with a single tool.On the other hand, the recently proposed stoppers have a seriousdisadvantage:

The fundamental purpose of a stopper is to protect the bead at leastmainly carrying out the sealing function against excessive deformationsduring operation of the engine, a purpose which can only be fulfilled ina highly inadequate way by a stopper which is elastically and/orplastically deformable to a considerable extent during operation of theengine. If the stopper is formed by a bead enclosing the combustionchamber opening in the shape of a circular ring or by several such beadsarranged concentrically with each other, the cylinder head gasketclamped between engine block and cylinder head is unable to offer anyconsiderable resistance to the flattening of the beads (not taking intoaccount the stiffness of the beads), as a displacement (in the radialdirection with respect to the combustion chamber opening) of the area ofthe sheet metal layer surrounding the combustion chamber opening, whichoccurs along with the flattening of the beads forming the stopper,cannot be prevented in these known cylinder head gaskets. Thesedisadvantages also apply to the stopper disclosed in DE-C-199 34 825consisting of a ring of lugs punched out at three of their sides andbent alternately upwards and downwards out of a sheet metal layer.

The object underlying the invention was to create an at leastsubstantially metallic cylinder head gasket wherein when manufacturingthe device for delimiting the deformation (stopper), the attaching of ametal ring or the flanging of a sheet metal layer can likewise bedispensed with, but wherein the device for delimiting the deformationcan fulfill its main purpose, namely that of preventing excessivedeformation or flattening of a bead mainly carrying out the sealingduring operation of the engine better than the above-described knowndevices for delimiting the deformation consisting of one or severalbeads or ribs and grooves concentrically enclosing the combustionchamber opening.

SUMMARY OF THE INVENTION

Departing from a cylinder head gasket with such a device for delimitingthe deformation, i.e., a cylinder head gasket of the kind mentioned atthe outset, wherein the device for delimiting the deformation is formedin a sheet metal layer of the gasket plate by such a deformation of thesheet metal layer that the latter has elevations and depressions in itsmain surfaces in the area of the device for delimiting the deformation,and the thickness of the device for delimiting the deformation isgreater than the original thickness of the undeformed metal sheet of thesheet metal layer, i.e., for example, the thickness of the sheet metallayer in an area of the sheet metal layer bordering directly on thedevice for delimiting the deformation, this object is accomplished bymeans of a sheet metal layer provided with the device for delimiting thedeformation, which is designed in accordance with the invention, suchthat in sections through the sheet metal layer along circularcylindrical surfaces coaxial with the combustion chamber opening, thedevice for delimiting the deformation respectively has a row of discreteelevations following one another in a circumferential direction of thecombustion chamber opening and joined to one another in the respectivecircular cylindrical surface by the sheet metal of the sheet metallayer, and corresponding depressions lying directly opposite theseelevations in the sheet metal layer, with the shape of the elevationsdiffering from the shape of circular arcs at least partially enclosingthe combustion chamber opening in a plan view of the sheet metal layer,and the total area occupied by the elevations being at least equal tohalf of the total area of the device for delimiting the deformation andpreferably considerably larger than 50% of this total area. The areaoccupied by an elevation (in a plan view of the sheet metal layer) is tobe understood as the total area of all those portions of the sheet metallayer which were deformed when producing the elevation by deforming thesheet metal layer, i.e., which project out of the plane defined by thesheet metal layer prior to its deformation.

The device for delimiting the deformation according to the inventionalso differs from a modification of the device for delimiting thedeformation known from WO 98/28559, which consists ofcircular-arc-shaped beads which do not extend exactly concentricallywith the combustion chamber opening, so that one or several beadsimmediately adjacent to the combustion chamber opening do not formcomplete circles—in such a modification the elevations also formcircular arcs at least partially enclosing the combustion chamberopening in a plan view of the sheet metal layer.

In a cylinder head gasket according to the invention the said sheetmetal layer can be provided on its one main surface only with elevationsand on its other main surface only with depressions. Embodiments are,however, also possible wherein both elevations and depressions areprovided on each of the two main surfaces of the sheet metal layer, withthe depressions on the one main surface lying directly oppositeelevations on the other main surface. In any case, each depressioncorresponds in its shape to the elevation lying opposite it.Furthermore, under a predetermined specific pressure load on the gasket(pressure force per surface unit of the gasket plate) in the ring areaof the gasket plate occupied by the stopper and the bead which is to beprotected by the stopper, the elastic and/or plastic deformability inthe height of the elevations of the stopper should be smaller andpreferably less than approximately 50% of the deformability in theheight of the bead which is to be protected by the stopper. If oneregards the device for delimiting the deformation (stopper) and the beadto be protected by it as each being a spring which is capable ofdeformation perpendicularly to the plane of the sheet metal layer, thenthe spring constant (i.e. the hardness) of the device for delimiting thedeformation should be greater than that of the bead which is to beprotected.

When reference is made hereinabove to the thickness of the device fordelimiting the deformation, this thickness is defined by the spacingbetween the two parallel planes which in the area of the device fordelimiting the deformation can be placed against the two sides of thedevice for delimiting the deformation on either side of the sheet metallayer. The above-mentioned discrete (or single) elevations are, ofcourse, joined to one another by areas of the sheet metal layer, and thebase or bottom of an elevation can pass over directly into the base orbottom of a neighboring elevation. Regarding the percentage area of thedevice for delimiting the deformation which is occupied by theelevations, the percentage areas of all elevations are, of course, to beadded, also when they project from both sides of the sheet metal layer(the latter is, so to speak, to be viewed as being transparent when itis a question of determining the percentage area occupied by theelevations).

In the cylinder head gasket according to the invention, the material ofthe sheet metal layer in the area of the elevations should becold-worked by deformation up to almost the breaking limit. In otherwords, under the pressure forces acting on the elevations duringoperation of the engine, the elevations should be at least almostinelastic and have at least almost no plastic properties.

Differently from the devices for delimiting the deformation according toWO 98/28559 and DE-U-298 04 534, a cylinder head gasket according to theinvention is characterized in that in sections through the said sheetmetal layer along circular cylindrical surfaces coaxial with thecombustion chamber opening, the crests of the elevations to be pressedagainst a neighboring sealing surface when the gasket is installed formwith this sealing surface a contact zone which encloses the combustionchamber opening but is interrupted several times, and, in particular,regularly in a circumferential direction of the combustion chamberopening, and the above-mentioned sealing surface is to be understood asa main surface of another sheet metal layer of the cylinder head gasketor a sealing surface of cylinder head or engine block against which thecylinder head gasket rests.

The inventive device for delimiting the deformation does not necessarilyhave to surround the combustion chamber opening as a ring-shapedstructure closed within itself. In the case of combustion chambers lyingvery close together, the web lying between two combustion chamberopenings in the sheet metal layer may be too narrow to also form thedeformation delimiting device in the area of this web.

In order to achieve a particularly high resistance of the deformationdelimiting device to deformation, in preferred embodiments of thecylinder head gasket according to the invention, the elevations areapproximately rectangular or trapezoidal in cross section and in a planview of the sheet metal layer preferably border on one another with atleast almost no spacing between them. The rectangular or trapezoidalshape of the elevations is preferably achieved by the elevations firstbeing produced with a larger height than their final height and thenbeing flattened off somewhat by reverse deformation. This results in ahigher stiffness of the elevations because the proportion of cold-workedzones and the degree of deformation of the sheet metal layer in the areaof the elevations are increased.

In a first group of particularly advantageous cylinder head gasketsaccording to the invention, the device for delimiting the deformationforms in a plan view of the said sheet metal layer a two-dimensionalpattern of single discrete elevations, and in a plan view of the sheetmetal layer the spacings between neighboring elevations are considerablysmaller (in particular, 50% or less) than the maximum diameters of theelevations. The elevations preferably form a regular pattern at least insome areas of the device for delimiting the deformation, but thegeometry of the engine block or cylinder head may also necessitate anoverall irregular pattern. In order to be able to work with a tool whichis as easy to manufacture as possible, when producing the elevations anddepressions, it is recommended that all elevations (and thus also alldepressions) be of approximately the same design, preferablyknob-shaped. A particularly dense “packing” of the elevations and thus adeformation delimiting device which is particularly resistant todeformation are obtained when the elevations form a honeycomb pattern ina plan view of the said sheet metal layer. With a view to obtaining apacking which is as dense as possible, it is also recommendable toprovide all elevations on one side of the sheet metal layer.

In the case of multilayer metallic cylinder head gaskets it is known perse to stamp a pattern of knob-shaped elevations in one or several metallayers (EP-A-0 470 790, FIG. 7). On the one hand, however, the solepurpose of these elevations is to minimize the heat transfer betweenengine block and cylinder head by the metal layers of the cylinder headgasket being kept at spacings from one another also when the cylinderhead gasket is installed, and, on the other hand, the spacings betweenneighboring elevations are larger than the maximum diameters of theelevations, so that such a knob-like pattern does not possess theresistance to deformation that is desired for a device for delimitingthe deformation.

In a second group of cylinder head gaskets according to the invention,the sheet metal layer provided with the device for delimiting thedeformation is designed such that the elevations are formed by at leastone bead which in a plan view of the sheet metal layer surrounds thecombustion chamber opening in an almost closed configuration and formsover at least part of its length a meander extending in acircumferential direction of the combustion chamber opening. Such anembodiment makes it possible to form a second sealing location,preferably radially (with respect to the combustion chamber opening)within the bead mainly carrying out the sealing function, as such adevice for delimiting the deformation can form with a neighboringsealing surface a closed contact zone around the combustion chamberopening when the bead forming the deformation delimiting devicesurrounds the combustion chamber opening in closed configuration. Atlocations where an opening, for example, a combustion chamber or anopening for the passage of cooling water or lubricating oil, lies in theimmediate vicinity of a combustion chamber in the engine to be sealed,the bead forming the deformation delimiting device cannot have ameandering course in the area between the combustion chamber and thesaid opening, but instead, for example, a straight-lined orcircular-arc-shaped course. A correspondingly dense “packing” of themeander loops results in a deformation delimiting device which is muchmore resistant to deformation than the above-described deformationdelimiting device according to WO 98/28559 and DE-U-298 04 534, alsowhen the percentage area of the deformation delimiting device occupiedby the meandering bead—measured in a plan view of the sheet metallayer—is smaller than half the total area of the deformation delimitingdevice measured in this plan view. Such meandering beads are thus alsoto be regarded as falling within the invention.

In a third group of cylinder head gaskets according to the invention,the deformation delimiting device is designed such that in a plan viewof the said sheet metal layer the elevations are formed by a ring ofbeads enclosing the combustion chamber opening, with the beads extendingapproximately in the radial direction with respect to the combustionchamber opening. With such a bead configuration a flattening of thebeads would at least not involve any appreciable radial displacement ofthe beaded area of the sheet metal layer (in contrast to a deformationdelimiting device with one or several beads, each of which encloses thecombustion chamber opening in the shape of a ring).

In preferred embodiments of the invention, when producing the elevationsand depressions the material of the sheet metal layer is deformed to asgreat an extent as possible, namely almost as far as the breaking limit,and cold-worked. Steels with a tensile strength of approximately 600 toapproximately 1,800 N/mm², preferably from 700 to 1,700 N/mm², aresuitable for the sheet metal layer provided with the stopper—below thatthe material would be too soft, a higher tensile strength would impairthe deformability. It should be noted that the tensile strength of thestarting material need not necessarily lie in this range, but rather thetensile strength of the finished product. The desired hardness may beachieved by a heat treatment following the deformation, however, thedesired hardness is preferably achieved by cold-working. Band steeltypes 1,4310 according to the European standard EN 10088-2 areparticularly well suited.

The stopper is preferably produced on a so-called functional layer,i.e., on a spring steel layer in which the bead mainly carrying out thesealing function also is or was produced. In the case of multilayermetallic cylinder head gaskets, however, the stopper can also beprovided on another layer, as is disclosed in the prior art on cylinderhead gaskets. In the case of a multilayer metallic cylinder head gasketit is recommended not to provide the stopper on one of the outer layers,but on a sheet metal layer lying inside the stack of layers, so as toeliminate the danger of the elevations pressing into the sealing surfaceof the engine block or the cylinder head, above all, when the cylinderhead, as is customary in modern engines, is made of a light metal alloy.It is also for this reason that elevations with flat crests arerecommended.

An elevation pattern which is as dense as possible is aimed at (insofaras this permits deformation of the sheet metal layer), so as make theproportion of the total supporting area of the stopper as large aspossible. With this in mind, it may also be recommendable to fill thegaps between the crests of the elevations and possibly also thedepressions corresponding to the elevations with a filler, inparticular, with a casting resin or elastomeric material provided withfillers.

The height of the elevations preferably lies in a range of 5 to 25hundredth mm, in particular, 5 to 15 hundredth mm. If the elevations areprovided in an outer surface of the cylinder head gasket facing thecylinder head, and the cylinder head consists of a light metal alloy, itmay, however, be recommendable to make the elevations up to 30 hundredthmm high, in order to take into account any possible embedding of theelevations in the sealing surface of the cylinder head.

Sheet metals with a thickness of 0.10 to 0.50 mm, preferably 0.20 to0.30 mm, are particularly well-suited for the sheet metal layer providedwith the stopper.

Since it is particularly recommendable to produce the elevations anddepressions by deep-drawing of the sheet metal, the elevations ofpreferred embodiments have flanks extending at an incline to the planeof the sheet metal layer, which results in approximately trapezoidalcross sections.

As mentioned above, the aim is for the elevations to have as large a“packing density” as possible. It is, therefore, recommended that theelevations be made as small as possible in a plan view of the sheetmetal layer (as small as the selected deformation process permits).

In view of the aim of achieving as large a “packing density” as possibleand the limit set by the material for deformation of the sheet metal,embodiments are preferred in which the elevations all point in the samedirection, i.e., project from the same main surface of the sheet metallayer. However, embodiments are, of course also possible in which theelevations point, in particular, alternately in both directions.

As mentioned above, in modern engines through-openings for coolingwater, oil and the like are often located in the immediate vicinity of acombustion chamber, so that in areas around a combustion chamber openingin a cylinder head gasket there is little space for accommodating asealing bead and a stopper. The same applies to combustion chamberopenings lying close together. This can cause considerable difficultiesin the above-described known cylinder head gaskets in which the stopperis formed not only by one but by several concentric beads. In thisrespect, the invention offers a further advantage when the stopper isformed by a pattern of small knob-like elevations, as it is then readilypossible to provide a constricted portion of the knob pattern in such anarrow area of the cylinder head gasket. The ring-shaped band formed bythe knob-like pattern can also be designed so as to be variable in itswidth, i.e., have a width profile, so as to take into account thefluctuations in the specific surface pressure of the gasket around acombustion chamber. The same applies accordingly to embodiments withmeandering beads or a ring of beads extending approximately radially.

In comparison with known stoppers consisting of one or several beads,which enclose the combustion chamber opening in the shape of a ring, theinvention offers yet a further advantage, in particular, when thestopper is formed by a pattern of knob-like elevations: A bead issupported on neighboring surfaces, on the one hand, only by itsline-shaped crest and, on the other hand, only by its two line-shapedbead feet, whereas in a stopper according to the invention the patternof the supporting surfaces is very much denser so that for this reasonalone a stopper according to the invention can offer a much greaterresistance to reverse deformation than a stopper consisting of one orseveral beads enclosing the combustion chamber opening in the shape of aring.

In cylinder head gaskets according to the invention, the stopper formsin a plan view of the sheet metal layer an area in the form of a bandwith a width preferably lying between 0.8 and 5 mm, in particular,between 1 and 3.5 mm, which encloses the combustion chamber opening atleast almost in the shape of a ring. In this plan view, this band isrespectively delimited (radially outwardly and inwardly with respect tothe combustion chamber opening) by a continuous line formed by a curveor line curved as little as possible and forming a tangent to theradially outward or inward elevations or elevation portions of thestopper. This is referred to mathematically as envelope or envelopecurve or envelope of the elevations. The surface of the band defined bythe two envelopes, measured in the plan view, is to be seen as the totalsurface of the deformation delimiting device.

In particularly advantageous embodiments of the invention, the stopperlies between the bead mainly carrying out the sealing function and thecombustion chamber opening (in principle, the stopper or a furtherstopper could also lie radially outside the said bead), above all,because the bead mainly carrying out the sealing function is then betterprotected from the high temperatures prevailing in the combustionchamber.

When the stopper disclosed in WO 98/28559 and discussed hereinabove issubjected to pressure and thereby undergoes flattening, the radialdisplacements of the sheet metal layer with respect to the combustionchamber opening outweigh its displacements in a circumferentialdirection of the combustion chamber opening, whereas the relations areexactly the reverse in a stopper according to the invention.

However, since radial displacements of the sheet metal layer cannot betotally excluded when stamping or deep-drawing the elevations formingthe stopper according to the invention, it is recommended that the finalcontour of the combustion chamber opening only be punched out after thestopper has been made from the sheet metal layer. It may readily occurthat parts of the initially produced stopper are punched on or away sothat a stopper consisting of knob-like elevations can have, for example,such punched-on, knob-like elevations, and in the case of a stopperformed by a meandering bead the radially inward loops (U-shaped areas ofthe meandering bead in a plan view) can be totally or partly missing.

It is known to provide a stopper with a height and/or width varyingaround a combustion chamber opening, in order to even out the specificsurface pressure around a combustion chamber opening. This principlecan, of course, also be applied to a stopper according to the inventionso that, for example, the height of its elevations varies around thecombustion chamber opening.

Further features, advantages and details of the invention will beapparent from the following description and the appended drawings ofparticularly advantageous embodiments of the cylinder head gasketaccording to the invention and of a preferred deep-drawing tool forproducing a stopper according to the invention by a type ofdeep-drawing—the invention thus also relates to such a tool and to aprocess for producing a preferred embodiment of the stopper according tothe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a plan view of a cylinder head gasket according to theinvention, which may be a gasket for a single-cylinder engine or aso-called single gasket for a multicylinder engine—in such multicylinderengines with single gaskets a separate cylinder head gasket is providedfor each combustion chamber so that several single gaskets lyingalongside one another are clamped between engine block and cylinderhead;

FIG. 2 shows a section from FIG. 1, which illustrates on an enlargedscale an area of the stopper shown in FIG. 1;

FIG. 3 shows a section along line 3-3 in FIG. 1 together with a planview of two elevations illustrated in FIG. 3 and a plan view of twodepressions recognizable in FIG. 3;

FIG. 4A shows a schematic plan view of a section of an upper part of adeep-drawing tool according to the invention for producing theelevations shown in FIGS. 1 to 3; and

FIG. 4B shows a plan view of a corresponding section of a lower part ofthis deep-drawing tool;

FIGS. 5 and 6 show plan views of an area of cylinder head gasketsaccording to the invention for a multicylinder engine with stopperssimilar to that according to FIGS. 1 to 3;

FIGS. 7 to 16 show sectional illustrations corresponding to FIG. 3through ten further embodiments of the cylinder head gasket according tothe invention;

FIGS. 17 and 18 show two further embodiments of a deformation delimitingdevice according to the invention; and

FIG. 19 shows an illustration, corresponding to FIG. 5, of a variant ofthe embodiment according to FIG. 17.

DETAILED DESCRIPTION OF THE INVENTION

The cylinder head gasket illustrated in FIG. 1 has a gasket plate 10consisting of a single sheet metal layer 12 (see also FIG. 3), out ofwhich an at least substantially round combustion chamber opening 14 andscrew openings 16 for the passage of cylinder head screws have beenpunched. The center or axis of the combustion chamber opening 14 isdesignated 18. The combustion chamber opening 14 or the associatedcombustion chamber is sealed off to prevent combustion gases fromescaping at least substantially by a bead 20 which, in the illustratedcase, is a so-called full bead surrounding the combustion chamberopening 14 as a closed circular ring concentric with the combustionchamber axis 18. During operation of the engine, with the gasketinstalled, the bead must be able to be flattened by elastic deformationin a spring-like fashion perpendicularly to the gasket plate 10. Forthis reason the sheet metal layer 12 consists of sheet spring steel.

In order that the bead 20 will not be excessively flattened under theinfluence of the pressure forces generated by the cylinder head screwsand the periodically fluctuating pressures occurring during operation ofthe engine (otherwise cracks might occur in the area of the bead 20 inthe sheet metal layer 12 during operation of the engine and the beadmight lose the necessary elastic properties), the sheet metal layer 12has been provided with a device for delimiting the deformation, which,as is customary, will be referred to in the following as stopper and isgenerally designated 22. In a plan view of the gasket plate 10 or thesheet metal layer 12, the stopper 22 has the shape of a ring-shaped bandwhich encloses the combustion chamber opening 14 and is preferablyarranged between the bead 20 and the edge of the combustion chamberopening 14. In the illustrated preferred embodiment, the stopper 22borders almost directly on the edge of the combustion chamber opening14.

In the embodiment illustrated in FIGS. 1 to 3, the stopper 22 consistsof a regular pattern of knob-like elevations 24 all of which have atleast approximately the same shape and project from the same side, i.e.,the main surface of the sheet metal layer 12. There is located directlyopposite each of the elevations 24 a depression 26 whose shapecorresponds to the shape of the associated elevation 24. As is apparentfrom FIG. 2, the elevations 24 form a so-called honeycomb pattern, whichensures the highest “packing density” of the elevations 24, i.e., thelargest possible number of elevations per surface unit of the sheetmetal layer 12.

As is apparent from FIG. 3, the elevations 24 project above the samemain surface of the sheet metal layer 12 as the bead 20, so that thelower side of the sheet metal layer in accordance with FIG. 3 is overallflat, at any rate in the area of the sheet metal layer illustrated inFIG. 3, if one disregards the depressions 26 and the concave side of thebead 20. In this case, the height A of the elevations 24 is smaller thanthe height B of the bead 20, so that the bead height is elasticallyreducible, but it is not possible for the bead to be excessivelyflattened if the resistance of the elevations 24 to deformation,measured in the direction perpendicular to the gasket plate 10 issufficiently large. It is essential that the total thickness C of thestopper 22 be larger than the thickness D of the sheet metal layer 12 inan area of the sheet metal layer immediately adjacent to the stopper 22,but less than the total thickness E of the deformed sheet metal layer inthe area of the bead 20.

In accordance with the invention, in the cutting plane of FIG. 3, in aplan view of the sheet metal layer 12 the maximum diameter G of eachelevation 24 is larger, preferably considerably larger than the spacingF between two neighboring elevations 24. The aim is for this spacing Fto be as small as possible, namely as small as the deformationproperties of the material of the sheet metal layer 12 will stillpermit. In the case of a sheet spring steel with a sheet thickness of0.2 mm, the maximum diameter G is, for example, 0.7 mm and the spacingF, for example, 0.2 mm—in this case, the smallest diameter H of eachdepression 26 is 0.2 mm (measured in the cutting plane of FIG. 3 andseen in a view of the sheet metal layer 12 in accordance with FIG. 3from below).

As is particularly clear from FIG. 2, the elevations 24 form a regularhoneycomb pattern which results in the largest possible “packingdensity” of the elevations. The depressions 26 then form a correspondinghoneycomb pattern (in a view of the sheet metal layer 12 in accordancewith FIG. 3 from below).

In sections through the sheet metal layer 12 along circular cylindricalsurfaces 30 coaxial with the combustion chamber axis 18, which areindicated by dot-dash-lines in FIG. 2, the stopper 22 forms a row ofsingle discrete elevations 24 following one another in a circumferentialdirection of the combustion chamber opening 14, and a corresponding rowof discrete depressions 26, respectively, and in a plan view of thesheet metal layer the spacing between neighboring elevations is lessthan the maximum diameter of these elevations. This fundamental featureof the invention is particularly clearly shown in FIG. 2.

In a modification of the embodiment illustrated in FIGS. 1 and 2, thepattern formed by the elevations 24 can also be of such orientation asto obtain rows of elevations 24 following one another in acircumferential direction of the combustion chamber opening 14, withthese rows forming circular rings concentric with the combustion chamberaxis 18. In this case, in sections through the sheet metal layer 12along circular cylindrical surfaces 30 coaxial with the combustionchamber opening 14, the spacing between elevations following one anotherin a circumferential direction of the combustion chamber opening is lessthan the maximum diameter of the elevations measured in this direction.

As is apparent from FIG. 2, in embodiments with knob-like elevations,the invention can also be defined with respect to the spacings of theelevations from one another by the spacing between neighboringelevations being less than the minimum diameter of the elevations attheir base, from which the respective elevation projects from the sheetmetal layer, in a plan view of the sheet metal layer.

The tool used for manufacturing the stopper 22 is shown schematically inFIGS. 4A and 4B. This tool is a kind of deep-drawing tool with a toolupper part and a tool lower part, between which the sheet metal layer 12is inserted, and the two tool parts are then pressed against each other.FIG. 4A shows a section from a plan view of the side of the upper partof the tool facing the lower part of the tool, FIG. 4B a section from aplan view of the side of the lower part of the tool facing the upperpart of the tool. Depressions (or openings) 24 a forming a regularhoneycomb pattern have been machined in the side of the upper part ofthe tool illustrated in FIG. 4A, while pin-like elevations 26 aextending perpendicularly to the drawing plane of FIG. 4B and likewiseforming a regular pattern are provided on the side of the lower part ofthe tool illustrated in FIG. 4B, and the axes of the elevations 26 acoincide with the axes of the depressions 24 a when the two tool partsare brought together in the direction of these axes, so that theelevations 26 a penetrate the depressions 24 a. Taking intoconsideration the dimensions indicated hereinabove in conjunction withFIG. 3, the spacings K drawn in FIG. 4A are 0.9 mm. Alternatively, astopper according to the invention can, however, also be made byprocesses which work with stamping rolls and are known, for example, bythe terms roller deformation and knurling.

FIGS. 5 and 6 show embodiments in which the width of the stopper aroundthe combustion chamber opening varies, only a portion of a singlestopper being illustrated in detail in each of the two Figures. In bothcases, several combustion chamber openings 14′, screw openings 16′ andwater through-openings 17′ are formed in a sheet metal layer 12′, andthe stoppers 22′ according to the invention are formed in both cases bya pattern of knob-like elevations 24′. As the final contours of thecombustion chamber openings 14′ were punched out after the knob-likeelevations 24′ were produced by deformation of the sheet metal of thesheet metal layer 12′, the stoppers 22′ also include elevations 24′which have been partially punched away and are therefore incomplete. Inthe embodiment according to FIG. 5, the knob-like elevations 24′ form aregular pattern, which, as is apparent from FIG. 5, results in gaps inthe knob pattern within the stopper 22′. In the embodiment according toFIG. 6, on the other hand, the knob-like elevations 24′ form area-wisesuch an irregular pattern that gaps are thereby avoidable in the knobpattern within the stopper 22′.

The envelopes of the stopper are designated A and B in FIGS. 5 and 6.

Further preferred embodiments of the cylinder head gasket according tothe invention will be explained in the following with reference tosectional illustrations corresponding to FIG. 3 in order to show thatthe invention is also applicable to multilayer cylinder head gaskets andthe stopper need not necessarily be provided on that sheet metal layerwhich comprises that bead or those beads serving mainly to seal around acombustion chamber. In all FIGS. 7 to 16 the combustion chamber openingextending through all layers of the respective cylinder head gasket isagain designated 14.

FIG. 7 shows a two-layered cylinder head gasket with two sheet metallayers 40 and 42 arranged on one another. The sheet metal layer 40 is aso-called functional layer consisting of sheet spring steel, in which abead 44 substantially assuming the sealing function is formed at aradial spacing from the combustion chamber opening 14, while the sheetmetal layer 42 is a sheet steel layer which under operating conditionsdoes not have any appreciable elastic or plastic properties at least inthe area of two stoppers 46 and 48. The stoppers 46 and 48 correspond tothe stopper 22 of the embodiment according to FIGS. 1 to 3, so that nofurther explanations in this respect are required. The bead 44 projectsin the direction towards the sheet metal layer 42, the elevations of thestoppers 46 and 48 in the direction of the sheet metal layer 40. In thisembodiment, the bead 44 is supported radially inside and outside (withrespect to the combustion chamber opening 14) and thus protected againstinadmissibly high deformations during operation of the engine.

The cylinder head gasket illustrated in FIG. 8 is three-layered with twobeaded outer layers 40′ and 40″ and an intermediate layer 42′ providedwith stoppers 46′ and 48′. The intermediate layer 42′ corresponds to thesheet metal layer 42 of the embodiment according to FIG. 5, while theouter layers 40′ and 40″ correspond to the sheet metal layer 40 of theembodiment according to FIG. 7 and are each provided with a bead 44′ and44″, respectively. The elevations of the stoppers 46′ and 48′ allproject only in one direction above the one main surface of theintermediate layer 42′, but they are able to prevent undesirably highdeformations of the two beads 44′ and 44″ if the total thickness of thestoppers 46′ and 48′, respectively, is sufficiently large, as theintermediate layer 42′ is downwardly bendable radially inside andradially outside the crests of the beads 44′ and 44″ according to FIG.8.

FIG. 9 shows a further three-layered cylinder head gasket with two outerlayers 50 and 52 serving as functional layers and an intermediate layer54 which is offset at 56 around the combustion chamber opening 14 in thedirection towards the outer layer 50 and radially within a bead 50 a,projecting in the direction towards the intermediate layer 54, of theouter layer 50. Consequently, the ring area of the intermediate layer 54that is radially located within the offset 56 can function as stopperfor the bead 50 a. The outer layer 52 likewise has a bead 52 a whichprojects in the direction towards the intermediate layer 54 and islocated opposite the bead 50 a. In addition, the outer layer 52 hasradially within the bead 52 a a stopper 58 according to the invention,which, with the exception of one difference, corresponds to the stopper22 of the embodiment according to FIGS. 1 to 3 owing to the offset 56the elevations 58′ of the stopper 58 must be higher than the elevations24 of the embodiment according to FIGS. 1 to 3 by the amountcorresponding to the height of the offset 56, in order that the bead 52a will be protected in the same way against excessive deformations bythe stopper 58 as the bead 20 of the embodiment according to FIGS. 1 to3 by the elevations 24 of the stopper 22.

FIG. 10 shows a four-layered gasket with two outer layers 60 and 62 andtwo inner or intermediate layers 64 and 66, all the layers except theintermediate layer 64 being provided with a bead 60 a, 62 a and 66 a,respectively, enclosing the combustion chamber opening 14. Theintermediate layer 64 is offset at 68 radially within the bead 60 a inthe direction of the outer layer 60, so that the offset 68 can assume astopper function for the bead 60 a. The intermediate layer 66 isprovided radially within the bead 66 a with an inventive stopper 70 towhich the same is applicable as was said about the stopper 58, as thebead 66 a is pressed radially outside the offset 68 against theintermediate layer 64, but the stopper 70 lies radially within theoffset 68. Given appropriate dimensioning of the total height of thestopper 70, the latter can also assume a stopper function for the bead62 a of the outer layer 62—the precondition being that in the event ofmaximum pressing of the cylinder head gasket occurring during operationof the engine, when the radially inner area of the outer layer 60 restsagainst the radially inner area of the intermediate layer 64, the totalthickness of the gasket plate in the area of the stopper 70 has to be ofsuch size that the bead 62 a will not be excessively flattened.

FIG. 11 shows a cylinder head gasket which like the embodiment accordingto FIG. 7 is two-layered, but each of the two sheet metal layers 72 and74 of the embodiment according to FIG. 11 is provided with a bead 72 aand 74 a, respectively, and an inventive stopper 76 provided on thesheet metal layer 74 is designed so as to be able to protect both beadsfrom excessive flattening, for which only a corresponding height of theelevations 78 of the stopper 76 is required.

The embodiment illustrated in FIG. 12 serves to show that a stopperaccording to the invention can also be arranged radially outside of thebead or beads to be protected. This cylinder head gasket has two outerlayers 80 and 82 provided with beads 80 a and 82 a and an intermediatelayer 84 with a stopper 86 according to the invention to protect the twobeads projecting against the intermediate layer 84. In this embodiment,it may be expedient to design the stopper 86, differently from shown inthe drawing, such that it has elevations projecting towards both sides,with neighboring elevations projecting in opposite directions in a planview of the intermediate layer 84.

The cylinder head gasket illustrated in FIG. 13 has two outer layers 88and 90 serving as functional and stopper layers, and a smoothintermediate layer 92, against which beads 88 a and 90 a of the twoouter layers project. Each of the outer layers has radially within itsbead an inventive stopper 94 and 96, respectively, whose elevationsproject in the same direction as the bead of the respective outer layer.

FIG. 14 shows a three-layered cylinder head gasket with three functionallayers, namely two outer layers 98 and 100 and an intermediate layer102, each of which is provided with a bead 98 a, 100 a and 102 a,respectively. The intermediate layer 102 also has radially within thebeads a stopper 104 according to the invention. Given appropriatedimensioning of its total thickness and adequate flexibility of thelayer 102, the stopper 104 can protect all three beads against excessiveflattening.

The cylinder head gasket illustrated in FIG. 15 has four layers, two ofwhich are designed as functional layers and two as functional andstopper layers, namely two outer layers 106 and 108 and two intermediatelayers 110 and 112, each of which is provided with a bead 106 a, 108 a,110 a and 112 a, respectively. In addition, each of the intermediatelayers has radially within the beads an inventive stopper 114 and 116,respectively. If the elevations of the stopper 114 project sufficientlyfar (downwards in accordance with FIG. 15), they can protect the twobeads 106 a and 110 a against excessive deformations, and the sameapplies to the stopper 116 and the beads 108 a and 112 a.

The cylinder head gasket illustrated in FIG. 16 is five-layered and ofmirror-symmetrical design with respect to an intermediate layer 120. Theintermediate layer 120 is a smooth sheet metal layer, while two outerlayers 122 and 124 are beaded functional layers, and two intermediatelayers 126 and 128 are beaded functional and stopper layers, whoseinventive stoppers are designated 130 and 132. Given appropriatedimensioning of the total thickness of the stoppers 130 and 132,respectively, each of these stoppers can protect the beads of its ownand the neighboring sheet metal layer against excessive flattening.

Two further embodiments of the invention are illustrated in FIGS. 17 and18, which each show in perspective representation a section of a sheetmetal layer provided with a stopper according to the invention. Thesheet metal layer also has a bead substantially assuming the sealingfunction, but in a multilayer gasket this bead could also be provided inanother sheet metal layer. In both cases, the combustion chamber openingis again designated 14.

In the embodiment according to FIG. 17 the sheet metal layer 200 hasradially within the bead 202 substantially assuming the sealing functiona stopper 204 which is delimited by dot-dash lines 206 and 208, i.e.,the envelopes, which in this case both extend concentrically with thecombustion chamber opening 14. In the area of the stopper 204, the sheetmetal layer 200 is provided with a meandering bead 210 whose loops areradially oriented with respect to the combustion chamber opening 14 andpreferably lie as close together as is permitted by the forming behaviorof the material of the sheet metal layer 200. From FIG. 17 it isapparent that also in this embodiment—in a plan view of the sheet metallayer 200 and within the delimiting lines 206, 208—the area occupied bythe bead 210 is at least as large as, preferably larger than half thearea of the ring-shaped portion of the sheet metal layer 200 delimitedby the delimiting lines 206 and 208. In this connection, it is to benoted that when calculating the percentage area of the bead 210 withrespect to the total area of the stopper, i.e., the elevations of thisstopper 204, in a plan view of the sheet metal layer 200 all portions ofthe bead 210 must be included, i.e., also the surfaces of the two beadflanks between the bead crest and the undeformed portions of the sheetmetal layer 200.

In the embodiment according to FIG. 18, a sheet metal layer 200′provided with a bead 202′ has a stopper 204′ which is formed by a ringof beads 210′ extending radially with respect to the combustion chamberopening 14. As is apparent from FIG. 18, in accordance with theinvention the minimum spacing A between two neighboring beads 210′ issmaller, preferably considerably smaller than the minimum width B of thebeads measured in a plan view of the sheet metal layer 200′. In thisconnection, it is to be noted that the spacing of the beads from oneanother in a radial direction with respect to the combustion chamberopening 14 can increase outwardly. Alternatively or additionally, thebead width can increase outwardly in a radial direction. At theirradially outer ends, the beads 210′ pass with curvatures, i.e., withradii, into a flat area of the sheet metal layer 200′ in both a sideview of each bead and a plan view of the sheet metal layer (the latteris not clearly apparent from FIG. 18), so that in a plan view of thesheet metal layer the radially outer ends of the beads 210′ formapproximately a circular arc extending over 180°. The envelopes of thestopper 204′ are designated 206′ and 208′. If in the embodimentaccording to FIG. 18 the final contour of the combustion chamber opening14 is only punched out after the beads 210′ have been produced, itshould be ensured that, for example, by adequate supporting of the beadsin the punching tool, the radially inner ends of the beads do notundergo deformation to a very great extent. On the other hand, whenpunching out the final contour of the combustion chamber opening 14 ofthe embodiment according to FIG. 17 the total or partial punching awayof the radially inner arcs or loops of the meander formed by the bead210 could be tolerated.

FIG. 19 shows a variant of the embodiment according to FIG. 17, moreparticularly, a variant similar to the embodiment according to FIG. 5 orFIG. 6. The envelopes are, therefore, designated A′ and B′.

FIG. 19 shows a sheet metal layer 200′ with combustion chamber openings14′, screw openings 16′, water through-openings 17′ and beads 20′ whichenclose the combustion chamber openings 14′, pass over into one anotherin a web area between two neighboring combustion chamber openings 14′and are to be protected against excessive deformations by stoppers 204′according to the invention. The stopper 204′ shown in greater detail isformed by a meandering bead 210′ which surrounds the associatedcombustion chamber opening 14′ in closed configuration and varies in itsmeandering course in such a way that the stopper 204′ has a varyingwidth around the combustion chamber opening 14′. The reasons for thiswidth profile can be seen in the following: When openings, such as oneof the openings 17′, are provided in the immediate vicinity of acombustion chamber opening 14′ in the sheet metal layer 200′, theconfined spatial conditions can make constriction of the stopper 204′necessary. On the other hand, it may be recommendable to widen thestoppers 204′ in areas where two beads 20′ pass over into each other inthe web area between two neighboring combustion chamber openings 14′ andform a Y-shaped configuration.

As is apparent from the above, each inventive stopper has in a plan viewof the sheet metal layer a plurality of small radii, in the region ofwhich the material of the sheet metal layer is cold-worked, i.e., thepercentage area of the cold-worked portions is a great deal larger in astopper according to the invention than in a stopper according to WO98/28559. This is expressed in the sum of the arc angles of these radiiof a stopper seen in a plan view. In the case of the above-describedknown stoppers disclosed in WO 98/28559 and in DE-U-298 04 534, the sumof the arc angles is 360° multiplied by the number of circular beads,whereas the sums of the arc angles in the stoppers according to theinvention are calculated as follows: If the stopper is formed by apattern of knob-like elevations, the sum of the arc angles is 360°multiplied by the number of knobs; if the stopper has a bead surroundingthe combustion chamber opening in an at least almost closedconfiguration and having a meandering course over at least part of itslength, the sum of the arc angles is twice 180° multiplied by the numberof loops of the meander; and if the stopper is formed by a ring ofradially extending beads, the sum of the arc angles is 180° multipliedby the number of beads.

1. A cylinder head gasket with a gasket plate being at leastsubstantially metallic, said gasket plate comprising one or severalsheet metal layers and having several combustion chamber openings, eachof said combustion chamber openings having at least one first beadassociated therewith and being surrounded by said at least one firstbead formed in a sheet metal layer of said one or several sheet metallayers and having a spring rate so as to be elastically deformable inheight, wherein for delimiting the elastic deformation of said firstbead at least one delimiting device is associated with each of saidfirst beads, said delimiting device being close to the respective firstbead, surrounding the respective combustion chamber opening and beingobtained by deformation of the sheet metal layer or another sheet metallayer of said one or several sheet metal layers such that (a) saiddelimiting device is formed by at least one second bead of said deformedsheet metal layer, said second bead having a spring rate and, in a planview of said deformed sheet metal layer, surrounding the associatedcombustion chamber opening substantially completely and forming over atleast part of the length of said second bead a substantially completemeander extending in a circumferential direction of said combustionchamber opening; (b) all around the respective combustion chamberopening the spring rate of the second bead is greater than the springrate of the associated first bead when measured perpendicularly to saidgasket plate; (c) in plan view of said gasket plate, the second bead isdisposed between the associated combustion chamber opening and theassociated first bead; (d) the height of the second bead is selected soas to allow an elastic deformation of the associated first bead; and (e)in a plan view of the deformed sheet metal layer the total area occupiedby the second bead is at least equal to half of the total area occupiedby said delimiting device.
 2. The cylinder head gasket of claim 1wherein the second bead is obtained by such a deformation of saiddeformed sheet metal layer that a thickness of material of a portion ofsaid layer forming the second bead is substantially the same as athickness of material of the deformed layer adjacent said second bead.3. The cylinder head gasket of claim 1 wherein the height of the secondbead is selected such that when the gasket is tightened, the first beadis initially compressed without compression of the second bead.